Tamiflu-resistant swine flu strain emerges

July 9, 2009, 6:32 am

New Zealand health officials hope the diagnosis of a San Francisco teenager with a Tamiflu-resistant strain of swine flu is a random mutation of the virus.

"We will be asking the Pandemic Influenza Technical Advisory Group (PITAG) to have a look at this," deputy director of public health Fran McGrath told NZPA.
She hoped it would turn out to be a "point mutation" of the virus -- which can occur in a patient even if they are not taking the anti-viral drug.

The Health Ministry would ask its technical experts to talk to virologists and other specialists at the Centres for Disease Control, in the United States, "about any evidence of the sort that we're going to be worried about", she said.

There were two main possibilities: either the case in the 16-year-old American girl showed swine flu was capable of not only developing drug resistance but also spreading between humans in that resistant form, or it was a one-off point mutation.
Two other cases of swine flu resistant to Tamiflu had occurred in patients taking the drug in Japan and Denmark, but Dr McGrath said it would be good if the virus had not yet mutated to a form which could spread carrying the mutation.

"So far, these are looking like point mutations, which is good news," she said.
Arthur Reingold, a professor at the University of California's school of public health, told the San Francisco Chronicle the fact the teenager was not taking Tamiflu suggested she may have caught the resistant variant from somebody else.
But Dr McGrath said it was important to remember that the virus spreading in New Zealand was still capable of being treated with Tamiflu.

Since January 2008 seasonal A (H1N1) flu viruses have become resistant to Tamiflu.
So far, six samples of the swine flu A (H1N1) viruses have also been tested, and none had the mutation, which indicated they were still sensitive to the drug.

New Zealand had a fair way to go before having to deal with a resistant form with good transmissibility, but when that happened the next step would be to switch to another anti-viral, such as Relenza.

Dr McGrath said the factor which would influence any use of swine flu vaccine in NZ would be the pattern of infections and their severity.
"Right at the moment, there isn't a lot of reason why we'd want to short-circuit the normal licensing process," she said.
"Severity would be the key factor."

Two New Zealand scientists have said in a study published in the journal Eurosurveillance that the present form of swine flu may be at least 40 times less lethal than originally estimated.

Probably no more than one in 10,000 patients might die, and the toll might be as low as one in 1 in 100,000 patients, according to Nick Wilson and Michael Baker.

Prime Minister John Key said this week that the Government had ordered a stockpile of a new swine flu vaccine for healthcare staff and other emergency workers.
The Government has ordered 300,000 doses of a vaccine from Baxter Healthcare -- enough to give 150,000 people the required two doses -- and it will be delivered within a month.

But the licensing of the vaccine is likely to take until December.

The death of a Christchurch man yesterday took the total number of swine flu deaths in New Zealand to five.

Chief Coroner Neil MacLean said the 49-year-old victim, who was thought to have underlying respiratory problems, died at the weekend.
A 46-year-old Blenheim man who died at his home a week ago was the country's fourth linked death, said Dr McGrath.
"While he has tested positive for novel influenza A, he had pre-existing medical conditions," she said.
The number of confirmed cases of swine flu yesterday was 1272, but Dr McGrath said this was only a small sampling of the actual number of cases.
hat-tip Niman